Genetic Tests Already Becoming Obsolete

June 11, 2008

Genetic testing may be even worse than flat screens when it
comes to the speed at which they become out of date. Last fall, I took a genetic test for a
recently identified genetic variation linked to a significantly increased risk
of type 2 diabetes. With a family history of the disease and other risk
factors, I was curious about my own genetic status. Fortunately, I didn’t have
that high-risk allele–but given my family history, I likely have other
disease-linked variants.

At the Beyond Genome
conference in San Francisco
yesterday, I discovered that the test I took a year ago now screens for four
genetic variants that boost risk for the disease. Those new
additions are part of a flood of genome-wide association screens that have been reported over the past year. The rate may slow down as variants with the
biggest impact on common diseases are identified.

The test I took was focused on a single disease, type 2
diabetes. Genome-wide screens, such as those offered by Navigenics, DeCode,
and 23andMe, offer
updates–either included in the initial fee or for an annual subscription–to
their customers as additional information becomes available.

The issue led to an interesting panel discussion about who
is responsible for tracking patients who do show an increased risk for disease.
The problem is so new that there is no consensus yet. But Steve Murphy, founder of the personalized-medicine
practice Helix Health, argued that it is the physician’s job, just as it is his
or her responsibility to make sure that patients with high cholesterol and
other risk factors are properly monitored.

Here’s an unrelated but fascinating fact that you may have
heard before: a full 10 percent of fathers may not be the biological parent of
their children, according to Charles Lee, director of cytogenetics at the Harvard Cancer Center.
Lee’s group didn’t set out to examine these rates specifically–researchers do paternity
testing as part of their standard genetic-testing process. In the process, they
discovered that one in ten men are not the biological fathers of their children.